Integrated gasification combined cycles generate electric power, for example, with a driving force of a gas turbine that combusts a combustible gas generated by gasifying carbonaceous feedstocks, such as coal and biomass, and a driving force of a steam turbine obtained by recovering exhaust heat of the gas turbine. A representative includes an integrated coal gasification combined cycle (IGCC) using coal (for example, refer to PTL 1).
Generally, integrated gasification combined cycles are configured to include a carbonaceous feedstock supply device, a gasifier, a char recovery unit, a gas purification unit, gas turbine equipment, steam turbine equipment, and a heat recovery steam generator. In the gasifier, a carbonaceous feedstock is gasified by a gasification reaction and a combustible gas is generated. The combustible gas generated by the gasifier is purified by the gas purification unit after an unreacted portion (char) of the carbonaceous feedstock is removed in the char recovery unit, and is supplied to the gas turbine equipment.
The gas turbine equipment combusts the combustible gas with a combustor to generate a high-temperature/high-pressure flue gas to drive the gas turbine. The heat recovery steam generator recovers heat from the flue gas after driving the gas turbine, and generates steam. The steam turbine equipment drives the steam turbine with the steam generated by the heat recovery steam generator.
The related-art integrated gasification combined cycles include a gas cooler (syngas cooler) that generates steam from cooling water by heat exchange between the combustible gas generated by the gasifier and the cooling water. The cooling water subjected to heat exchange with the flue gas in a coal economizer of the heat recovery steam generator is supplied to the gas cooler. Additionally, the steam generated by the gas cooler is supplied to the steam turbine equipment after being supplied to the heat recovery steam generator and is furthermore turned into high-temperature/high-pressure steam. In this way, in the related-art integrated gasification combined cycles, the cooling water and the steam are circulated between the heat recovery steam generator, the gas cooler, and the steam turbine equipment.